How do i get my name off a loan that me and my ex took out over 2 yrs ago and i had thought my name was taken?

Off. My ex took out a loan over 3 yrs ago and i had put my name on it so he could get a loan large enough. When we broke up he told me my name was off so i never thought twice about it. I recently got a letter in the mail saying my payment from that loan was past due with his and my name on the letter and will be taken to collections. I got ahold of him and he told me he had lost his job and hadnt paid it. And he didnt take my name off and they told me theres no way i can get my name off he had to go reapply with only his name and he never did and now im getting sent to collections. What do i do???